The proposed research will study the mechanism by which the araC gene protein of the L-arabinose operon in Escherichia coli positively controls the operon. This will be done with in vivo studies on wild type and mutant cells, and with in vitro studies of the control region. Techniques will be developed for the rapid purification of large quantities of the araC gene protein and the ara control region of DNA. The physical properties of the purified elements in the ara control system-araC protein, ara DNA, RNA polymerase, and cyclic AMP receptor protein--and their interactions will be studied. A major objective will be to learn the relative positions of the araC protein, RNA polymerase, and cyclic AMP receptor protein binding sites in the control region. Genetic and physical studies will be directed toward this end. A fine-structure genetic map of the control region will be constructed. In vitro studies to determine the relative locations of the binding sites will include the chemical crosslinking of the proteins when they are bound to ara control region DNA and high resolution electron microscopy of the protein-DNA complex. In order to further define the binding locations of the proteins, the sequence of the 5' end of the messenger and the sequence of parts of the DNA will be determined from wild type and mutant cells.